Segmented laser apparatus and method of making the same

ABSTRACT

The apparatus comprises an outer jacket having a through bore which receives a plurality of laser discs therein. Spacing pins are provided between adjacent discs for spacing adjacent discs apart. Opposite edges of alternate discs are spaced from the wall of the bore to define fluid passages therebetween. Retaining means are sealingly received in each end of the jacket for retaining the laser discs within the jacket and for providing for the flow of energy and a fluid in and out of said jacket. The method includes forming a laser rod to a preselected diameter, removing a portion of the rod to provide a relieved surface and cutting the rod into a plurality of laser discs. The discs are placed into a jacket to provide the laser apparatus.

United States Patent Duffy et al.

[451 Oct. 3, 1972 [54] SEGMENTED LASER APPARATUS AND METHOD OF MAKINGTHE SAME [72] Inventors: Joseph .1. Duffy, Northport; Alexander S.Dunbar, Plainview, both of NY.

[73] Assignee: Hadron Inc., Westbury, NY.

[22] Filed: Aug. 21, 1970 [21] Appl. No.: 65,794

[52] US. Cl ..33l/94.5 [51] Int. Cl ..H01s 3/06 [58] Field of Search..33 l/94.5; 330/43 [56] References Cited UNITED STATES PATENTS3,487,330 12/1969 Gudmundsen ..331/94.5 3,500,231 3/1970 Tomiyasu et al...33 l/94.5 3,569,860 3/1971 Booth ..33l/94.5

Primary Examiner-William L. Sikes Attorney-Yuter & Fields [57] ABSTRACTThe apparatus comprises an outer jacket having a through bore whichreceives a plurality of laser discs therein. Spacing pins are providedbetween adjacent discs for spacing adjacent discs apart. Opposite edgesof alternate discs are spaced from the wall of the bore to define fluidpassages therebetween. Retaining means are sealingly received in eachend of the jacket for retaining the laser discs within the jacket andfor providing for the flow of energy and a fluid in and out of saidjacket.

The method includes fonning a laser rod to a preselected diameter,removing a portion of the rod to provide a relieved surface and cuttingthe rod into a plurality of laser discs. The discs are placed into ajacket to provide the laser apparatus.

16 Claims, 6 Drawing Figures PATENTEDnms I972 SHEET 1 OF 2 INVENTORSJOSEPH .z un-r ALEXANDER 5t DUN BAR "fix/w Arm/mars PATENTEflums m2 43,696,308

sum 2 0P2 SEGMENTED LASER APPARATUS AND METHOD OF MAKING THE SAME Thepresent invention relates generally to a laser construction and a methodof making the same and, more particularly, pertains to an efficientsegmented laser apparatus and to a method of fabricating the same.

As the use of laser apparatus becomes more and more widespread, thedemand for high power performance from laser systems continuouslyincreases. However, problems such as thermal-optical distortion, andreduced efficiency arise in attempting to utilize laser systems at highaverage powers. Moreover, in many cases extreme stresses are set up inthe laser rod which have caused the rod to fracture. The apparent sourceof most of these problems is the variation of thermal gradients in thesystem. More specifically, when a solid laser rod is cooled, thetemperature of the surface adjacent to the coolant will obviously belower than the surface further away from the coolant, thereby causingwide variations in thermal gradients within the rod which, in turn,cause optical deterioration and consequent fracture.

In order to ameliorate the situation, it has been proposed to utilize aplurality of discs as the laser rather than a solid rod, and to cooleach disc by causing a coolant to flow over the surfaces of the discs.Alternatively, it has been proposed to place the adjacent discs inspaced relationship to each other with a suitable cooling fluidtherebetween. These types of laser constructions, which are referred toas a segmented or, alternatively, an axial-gradient laser, substantiallyeliminates radial distortion of the beam and separates the laseraperture from its heat-transfer characteristics thereby permitting eachcharacteristic to be compensated for individually. While such segmentedlaser systems permit lasers to be operated at higher average powers thansolid rod laser systems, there are still many problems associated withfabricating such constructions. Foremost among these problems is theproblem of maintaining the discs in position with respect to each otherand with respect to the optical axis of the laser and, at the same time,to eliminate any strain on the discs caused by the holding or aligningstructure. Consequently, many such holding structures have been proposedbut each one has some type of disadvantage associated with its use suchas: failure to maintain the discs in their precise orientation, toocomplex a structure, or the system simply is not economical tofabricate. Another problem involves providing means for the introductionof the fluid or coolant into the laser array. Additionally, mostsegmented lasers must be handled very carefully or the discs may beknocked out of alignment by the slightest jar. This obviously places asevere limitation on the system since even the mounting of the array maycause misalignment of the discs.

Accordingly, it is an object of the present invention to provide animproved segmented laser apparatus.

A more specific object of this aspect of the invention is to provide asegmented laser apparatus in which the laser discs are reliablymaintained in a preselected orientation with respect to each other alongthe optical axis of the laser.

Another object of the invention resides in the novel details ofconstruction which provide a laser apparatus of the type described whichmay be handled in the same manner as a solid rod laser thereby reducingthe stringent handling requirements for such devices.

A further object of the invention is the provision of an efficient andeconomic segmented laser apparatus.

Another object of this invention is the provision of a high averagepower output segmented laser apparatus.

Accordingly, a segmented laser apparatus constructed according to thepresent invention comprises an outer jacket having an inner walldefining a through bore. A plurality of laser discs are received in saidthrough bore and spacing means is provided between adjacent ones of saidplurality of discs for maintaining the discs in spaced relationship toeach other. The pluralityof discs are sized and positioned so thatopposite portions of alternate ones of the plurality of discs are spacedfrom the wall to define fluid paths therebetween. Retaining means issealingly received in at least one end of the jacket for retaining theplurality of laser discs therein.

At present, many methods are utilized to fabricate segmented laserapparatus. However, these methods have disadvantages associated withtheir use such as poor quality control, use of complex equipment andhigh cost.

Accordingly, it is an object of this invention to provide an improvedmethod for fabricating a segmented laser apparatus.

A more specific object of this aspect of the invention is to provide amethod for accurately producing the laser discs comprising the segmentedlaser apparatus of the invention.

Another object of the invention is to provide a method for fabricating asegmented laser apparatus which is relatively simple to perform.

Accordingly, a method for fabricating a segmented laser in accordancewith the present invention comprises forming a laser rod to apreselected diameter. A portion of the rod is removed to provide arelieved surface on the rod and the rod is cut into a plurality ofdiscs.

Other features and advantages of the present invention will become moreapparent from a consideration of the following detailed description whentaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a vertical sectional view, with parts broken away, of asegmented laser apparatus constructed according to the presentinvention;

FIG. 2 is a front elevational view of a right-hand laser disc of thetype shown in FIG. 1;

FIG. 3 is a side elevational view thereof;

FIG. 4 is an exploded view, with parts broken away, of the laserapparatus of FIG. 1 illustrating the retaining portion of the apparatusin detail;

FIG. 5 is a diagrammatic view of the laser apparatus illustrating thepath of fluid flow across the face of the discs; and

FIG. 6 is a diagrammatic view of a modified embodiment of a laserapparatus illustrating a modified arrangement for maintaining the discsin alignment.

In the discussion which follows, reference will be made to variousmaterials which were utilized for fabricating an actual model of thelaser construction under consideration. However, it is to be noted thatthese references to materials are for illustrative purposes only and arenotto be interpreted as being a limitation on the present invention. Tobe more specific, the active laser portion of the laser discs describedhereinbelow comprise lithia-alumina silicate glass which is doped with 3percent neodymium. This material is manufactured by the Owens-Illinois,Inc. and is sold under the brand designation ED-2 laser glass. However,any other type of laser mediums such as glass, ruby, YAG, and the likecan be utilized, depending upon the energy output and wave lengthrequirements.

A segmented laser apparatus constructed according to the presentinvention is illustrated in FIG. 1 and is designated generally by thereference numeral 10. The apparatus includes an outer jacket 12 having acentral through bore 14. The outer jacket 12 may be. fabricated from anymaterial which will withstand laser pumping, such as Pyrex orthe like.However, in order to provide a relatively strong supporting tube orjacket for the laser discs, the jacket 12 may be fabricated from a glasssuch as ED-4 glass manufactured by Owens-Illinois, Inc. The ED4 glass isthe same basic composition as the ED-2 laser glass mentioned above, butis devoid of any neodymium. Alternatively, the jacket may be fabricatedfrom an ED-4S glass which is a highstrength form of ED-4 material. Inpractice, a solid rod of ED-4 or ED-4S glass is drilled so that thethrough bore 14 is of a preselected diameter. Thereafter, the bore isground and polished to a selected diameter. As noted hereinabove, thisexample of forming the outer jacket is for illustrative purposes onlyas-any tube may be utilized for the outer jacket.

Received within the jacket 12 are a plurality of righthand laser discs16 which alternate with a like plurality of left-hand laser discs 18.The right-hand laser discs 16 are identical in construction and areshown in greater detail in FIGS. 2 and 3. More specifically, the laserdisc 16 shown in these FIGS. comprises an inner optical portion 20fabricated from ED-4 laser glass, in the example chosen. Surrounding theinner active portion is an integral outer inactive portion 22 orso-called cladding which is of ED-4 material. The inner portion 20 isthe active laser portion of the laser discs while the outer inactiveportion 22 serves to support the laser portion. As shown" in FIG. 2, theright-hand edge 24 of the disc 16 is relieved for reasons which willbecome apparent from a consideration of the discussion below.

In practice, the discs 16 are fabricated from a solid laser rod. To bemore specific, the outside diameter of the rod is obtained by centerlessgrinding of the rod to the desired diameter. In order to obtain therelieved edge 24,the solid rod is moved to a new center positioned tothe left of the geometric center so that the geometric center of the rodis off-center with respect to the grinding device-The rod is then groundwhile in this off-centerposition to obtain the relieved edge. It is tobe noted that in addition to forming the relieved edge, a blendingoperation is simultaneously obtained. Moreover, this procedure ensuresthat each disc cut from the laser rod has an identical cross-section.

The rod is then sliced or cut at a preselected angle with respect to thegeometric axis of the rod to form each one of the laser discs 16. Theactual angle at which the discs are cut is determined by the respectiveindices of refraction at the interface between the laser disc and thefluid in which the disc is to be placed at the wavelength of interest.In other words, it is desirable that light enter and leave each disc atBrewster's angle to substantially eliminate reflection losses. Inaddition, the average direction of propagation of the beam should bealong the laser axis in order to avoid walk-off losses. Thus, theeffects of the refraction which occurs due to the beam entering thediscs at Brewsters angle must also be compensated. The light thusfollows essentially a zig-zag path through the assembly. This angle iseasily calculated from the relationship:

ADI/113+ B t/ w a=tanwhere:

A is the thickness of each disc;

B is the thickness of the fluid separating the discs;

n,,, is the index of refraction of the fluid;

n, is the index of refraction of the laser glass; and

a is the angle at which the discs are cut with respect to the geometricaxis of the rod.

After each laser disc has been cut from the rod the faces of the discsare polished. Additionally, the edges formed at the juncture of thecylindrical edges and the faces of the disc are blended to form a smoothcurve with a preselected radius of curvature. This blending may beperformed by a grinding operation or the like. Additionally, the facesof each disc are cut so that the faces are substantially parallel toeach other.

The left-hand discs 18 are formed in substantially the same manner asthe righthand discs 16, except that the rods from which the discs 18 areout are remounted on a center which is located to the right of thegeometric center of the rod to obtain the relieved edge rather than totheleft of the geometric center of the rod as is the case with theright-hand discs 16. Alternatively, a single rod may be utilized for therightand left-hand discs. However, for this latter case, the right-handand lefthand discs would be cut at a complementary angle with respect tothe geometric axis of the rod so that when positioned correctly withinthe outer jacket 12, the discs will be oriented at the correct angles toprevent beam walk-off.

It is to be noted that the discs 16 and 18 and the inner bore 14 of thejacket 12 are sized so that when the discs are received within the bore14, they will be in sliding engagement with the walls thereof, exceptfor the relieved edges which will be spaced therefrom to provide for theflow of a cooling fluid, as noted below.

The laser discs 16 and 18 are spaced from each other by spacing means toprovide a path for the flow of the fluid across the faces of each disc.To be more specific, after the faces of the discs .have been polished,three circumferentially spaced bores 26 are provided in the claddingportion 22 of the material, as shown in FIG. 2. The bores 26 arepositioned so that the axis of each one of the bores will besubstantially perpendicular to the face of the disc. Received within thebores 26 are respective pins 28. In practice, the pins 28 may be" vide athree-point support for adjacent discs of the apparatus.

It will now be obvious that the spacing means comprising the bores 26and the pins 28 and the sliding engagement between the discs 16 and 18and the walls defining the bore 14 maintain the laser discs 16 and 18 inproper rotational alignment with respect to the geometrical axis of thelaser array or apparatus. To be more specific, when each one of thediscs is properly located within the jacket 12 at the desired angle ofinclination to the geometrical axis, adjacent discs will rest on thethree-point support provided by the pins 28 of the preceding disc.However, if there is any rotational misalignment of the discs, the discswill tend to move away from their common three-point support. Thus, toensure that the discs are properly rotationally aligned, they are placedinto the outer jacket 12 and a slight pressure is applied to theoutermost discs to move all discs into rotational alignment. The discsare then maintained in this rotational alignment by retaining means,designated generally by the reference number 30, which is received ineach end of the jacket 12.

As noted hereinabove, a major advantage of a segmented laser apparatusis that each disc may be cooled by a suitable coolant thereby permittingthe apparatus to be operated at higher power levels. Thus, as shown inFIG. 5, the space between each disc provided by the pins 28 permits acoolant to flow across the faces of juxtaposed discs. Moreover, as notedhereinabove, opposite edges of alternate discs are relieved to providepaths for fluid or coolant to flow between the relieved edge of the discand the wall defining the bore 14 of the jacket 12. Thus, coolant orfluid flow through the jacket 12 will be from a relieved section or edgeof a disc, across the faces of adjacent discs, and around the relievededge on the opposite side of the adjacent disc. That is, as shown by thearrowheads 32 in F IG. 5, fluid flow will be around a relieved edge 24of a right-hand disc, across the faces of the juxtaposed discs, andaround the opposite relieved edge of the adjacent lefthand disc toprovide an efficient and effective means of cooling the laser discs.

The retaining device 30 is shown in detail in FIG. 4 and functions topermit energy to both enter and leave the laser discs or array in thejacket 12 and, in addition, provides the means for the entrance and exitof the cooling fluid which flows through the cavity or bore 14. Theretaining device 30 comprises the following elements (which aredescribed in greater detail hereinbelow): a stop and readout pilot 34, astop lockring 36, an O-ring 38, a prism holder 40, O-rings 42 and 44, aprism 46, and a prism lockring 48.

The stop and readout pilot 34 is provided with a through bore 50 anddiametrically opposed openended slots or notches 52 in the outer edge ofthe pilot. Additionally, the inner edge 54 is formed at an angle withrespect to the axis of the pilot to conform to the angulation of thelaser discs 16 and 18. In other words, the inner edges 54 of the pilotsat each end of the laser array of discs are at an angle such that thediscs will be maintained in their proper preselected angulation withrespect to the geometric axis of the laser when the pilots 34 arereceived in the jacket 12. Additionally, longitudinally extendinggrooves 56 are provided in the outer surface of the pilots 34 to providefor the flow of the fluid. Alternatively, the stop and readout pilots 34may be provided with relieved edges similarly to the discs 16 and 18 sothat the fluid may flow between the respective pilots and the walldefining the bore 14. The pilots 34 are sized so that they slidablyengage the wall defining the bore 14 and the bore 50 is sized so thatthe prism 46 is slidably received therein.

The stop lockring 36 includes rearwardly extending projections 58 whichare adapted to be received in the respective notches 52 in the pilot 34.Additionally, the stop lockring 36 is internally threaded at 60 toengage a complementary threaded portion of the prism holder 40. The stoplockring 36 and the pilots 34 provide a stop means to receive the prismholder 40. In other words, the pilot 34 will be maintained in properorientation because of the angulation of the edge 54 in contact with theangulated laser discs. Additionally, since the stop lockring 36 isseated in the notches 52 in the pilot, the lockring similarly will bemaintained nonrotatable within the jacket 12. Hence, the lockring andthe pilot provide a seat for the prism holder 40, as noted in greaterdetail below. The pilot 34, in practice, may be fabricated from the samematerial as the jacket 12.

The elements 40-48 provide a prism means which permits energy to flow toand from the laser discs by means of the prism 46 and also provides amount for the prism. More specifically, the prism holder 40 includes acentral through bore 62 which is of slightly greater diameter than theprism 46. Additionally, a shelf 64 is provided in the bore 62 to providea seat for the prism 46, as noted hereinbelow. The inner end 66 of theholder 40 is of reduced diameter and is provided with external threadsto threadably engage the threaded portion 60 of the lockring 36. Spacedradially extending flanges 68 and 70 are provided on the outer surfaceof the holder. The flange 68 is positioned so that it will be spacedslightly beyond the edge of the jacket 12 when the holder 40 is inposition. The outer end 72 of the holder 40 is externally threaded toreceive a complementary threaded portion of the prism lockring 48. Aplurality of spaced apertures 74 are provided through the wall of theholder 14 to permit fluid flow from the exterior to the interior of theholder.

The prism 46, in practice, is fabricated from the same material as thecladding 22. In other words, in the example under consideration, theprism 46 is fabricated from ED-4 glass. Hence, the rear face 76 of theprism 46 is formed substantially at Brewsters angle to the geometricaxis of the prism as determined by the indices of refraction of both theprism and the coolant at the interface of the face 76 and the coolantmedium. However, in order to compensate for any beam walkoff which maybe present from disc to disc in the laser array, the angle at which theface 76 is formed may be slightly in excess of Brewsters angle. On theother hand, the outer face 78 of the prism is formed at Brewsters anglewith respect to the geometric axis of the prism as determined by theindices of refraction of the prism and the fluid in which the outer faceis in contact. In practice, it is to be noted that the outer face 78will usually be in contact with air.

A radially extending flange 80 is provided on the prism which ispositioned adjacent the outer face 78 of the prism. The flange 80 issized and positioned so that it will seat on the shelf 64 in the bore62. As noted hereinabove, the diameter of the prism 46 is slightly lessthan the diameter of the bore 62 in the prism holder 40. However, flange80 is sized so that the prism will be coaxial with the prism holder 40when the prism is in position so that an annular space 84 (FIG. 1) willbe formed between the outer surface of the prism 46 and the innersurface defining the bore 62 of the holder 40. The length of the prism46 beyond the flange 80 is such that the prism will not extend beyondthe inner edge of the pilot 34.

The prism lockring 48 is internally threaded at 81 to engage thethreaded outer end 72 of the holder 40. Moreover, the outer edge of thelockring is provided with a radially inwardly extending wall 83 which isadapted to engage the flange 80 of the prism to force the prism flange80 rearwardly into abutment with the shelf 64 so that the prism ismaintained non-rotatable within the holder 40.

It is to be noted that alternatively the face 78 may be a plane-parallelouter face.

In the description of assembling the retaining device 30, only oneretaining device 30 will be referred to. However, it is to be understoodthat the retaining device at the other end of the jacket 12 will beassembled in a similar manner. Accordingly, after the laser discs 16 and18 have been centrally positioned in the jacket 12 in the manner notedhereinabove, the stop and readout pilot 34 is inserted and is rotated tothe correct position tomaintain the discs in their proper orientationand alignment. Thereafter, the stop lockring 36 is inserted into thejacket 12 so that the projections 58 are engaged in the notches 52. TheO-ring 38 is placed on the reduced diameter inner end 66 of the prismholder and the end 66 is threadedly engaged in the portion 60 of thelockring. The O-ring 38 is compressed between the shelf formed by thereduced diameter end portion 66 and the surface of the holder 40 and theouter end of the lockring 36 as shown in FIG. 1. Accordingly, expansionof the O-ring 38 causes the O-ring to engage the inner wall of the bore40 with sufficient pressure to lock both the discs 16 and 18 and thestop pilot 34 in place within the jacket tube. Moreover, it will benoted that the O-ring 38 also functions to substantially provide afluid-tight seal in the jacket 12 to prevent fluid from flowing aroundthe pilot 34 and thereby, out of the jacket. As noted above and as shownin FIG. 1, the flange 68 is spaced beyond the edge of the jacket 12 andis adapted to be engaged by an appropriate end-plate (not shown) whenthe apparatus is mounted within a laser system.

The O-ring 42 is placed on the prism 46 in abutment with the rearsurface of flange 80. The prism 46 is then inserted into the bore 62until the flange 80 is seated on the shelf 64. It is to be understoodthat the O-ring 42 is received between the flange 80 and the shelf 64.The O-ring 44 is placed on the other end 72 of the holder 40 against theflange 70. The prism lockring 48 is then threadedly engaged on thethreaded end 72 of the holder 40. The wall 83 engages the flange 80 andexerts a rearward pressure against the flange 80 to cause the O-rings 42and 44 to seal at their respective points. In other words, the ,O-ring42 effectively provides a seal between the flange 80 and the shelf 64,whereas the O- ring 44 provides a seal between the edge of the lockring48 and the flange and the wall of a through-bore in a laser head end capindicated by the dashed lines 71 which forms a part of the head mountingassembly (not shown). At this point, the prism lockring 48 may beloosened to permit the prism 46 to be rotated to the correctorientation. Thereafter, the lockring 48 is tightened to maintain theprism in this orientation.

In its assembled condition, as shown in FIG. 1, the laser apparatus 10of the present invention may be handled in the same manner and fashionas a solid laser rod. That is, the retaining means or device 30maintains the discs 16 and 18 immovable within the outer jacket 12 sothat the discs cannot fall out of alignment. The same comments apply tothe prism 46 which are securely locked in place by the respectivelockrings. Accordingly, the laser apparatus 10 may now be mounted in aconventional laser head and utilized in the same manner as any solidlaser rod. That is, energy may be pumped into the jacket 12 in theconventional manner and exit through the prisms 46. Additionally, acoolant fluid may be introduced into the jacket 12 through the apertures74 in the prism holder 40. The coolant flows through the annular space84 and through the grooves 56 in the pilot 34 into the jacket 12. Fluidflow is around the edges and across the spaces between the discs asnoted hereinabove in the description of FIG. 5. The fluid exits throughthe grooves 56 in the opposite retaining device 30 and the space 82therein and, finally, through the apertures 74 in the opposite holder40.

Accordingly, a segmented laser apparatus has been disclosed which iseasy to fabricate and which is highly efficient in operation. It shouldbe noted that a model of the subject laser apparatus has beenconstructed. utilizing the materials noted above and with the followingspecifications:

Coolant fluid Deuterium oxide Wavelength operation of laser l.06 micronsDiameter of active portion 20 of disc V4 inches Thickness of inactivecladding portion 22 3/ 16 inches Overall rod diameter 1. l 25 inchesAngle between face of disc and geometric axis of rod 48 39.5 Thicknessof each disc 0.250 inches Number of right-hand discs l8 Number ofleft-hand discs l8 Spacing between discs 0.025 inches Angle betweenouter face 78 and 57 I6 geometric axis of prism 46 Angle between innerface 76 and 52 20' prism 46 and geometric axis of prism Utilizing aPockels cell arrangement, the abovedescribed laser apparatus can be usedfor energy levels up to 60 kilowatts at 5 pulses per second and 12kilojoules per pulse.

FIG. 6 illustrates a modified embodiment of a laser apparatus utilizinga key and slot to maintain the laser discs in their preselectedorientation. More specifically, the left-hand laser discs 118 and theright-hand laser discs 116 are identical to the discs 16 and 18 with theexception that a key slot 86 is provided in the top surface of eachdisc. The key slot may be provided in the discs while the discs arestill in rod form, as noted hereinabove. A key 88 is provided which isadapted to be received in the key slot 86. The key 88 may be fabricatedfrom the dame material as the cladding 22 of the respective discs.Additionally, a key slot 90 is provided in the prism 146. It is to benoted that the prism 146 is identical to the prism 46 with the exceptionthat the prism 146 has a key slot 90. The key 88 is adapted to bereceived in the slot 90.

The slots 86 and 90 are positioned so that when the key is receivedtherein, the laser discs 116 and 118 and the prism 146 will be correctlyaligned with respect to each other and the geometric axis of thecomplete laser array comprising the discs and the prisms.

While preferred embodiments of the invention have been shown anddescribed herein, it will be understood that numerous omissions, changesand additions may be made in such embodiments without departing from thespirit and scope of the present invention.

What is claimed is:

l. A segmented laser apparatus comprising an outer jacket havingan-inner wall defining a through bore, a plurality of laser discs insaid bore, spacing means between adjacent ones of said plurality ofdiscs for maintaining said discs in spaced relationship to each other,opposite edges of alternate ones of said plurality of discs being spacedfrom said wall to define alternating fluid paths therebetween wherebyserial fluid flow is obtained through said jacket, and retaining meansreceived in at least one end of said jacket for retaining said pluralityof laser discs therein.

2. A segmented laser apparatus as in claim 1, in which said retainingmeans comprises fluid conduit means for providing a passage for the flowof fluid through said jacket.

3. A segmented laser apparatus as in claim 1, in which said retainingmeans includes prism means comprising a prism having a first faceextending beyond the edge of said jacket and angulated at the Brewsterangle determined by the prism and a fluid adapted to be in contact withsaid first face, and a second face received within said jacket andangulated at the Brewster angle determined by said prism and the fluidwithin said jacket, said prism means further comprising a prism holderhaving a through bore adapted to receive said prism therethrough, thediameter of said prism holder through bore being slightly in excess ofthe diameter of said prism whereby an annular fluid passage is formedtherebetween, means in said prism holder for providing for the flow of afluid to said annular passage, a radially extending flange on saidprism, a shelf in said prism holder adapted to provide a seat for saidflange, and sealing means between said shelf and 'said flange.

4. A segmented laser apparatus as in claim 1, in which said retainingmeans comprises stop means including a stop and readout pilot having arear edge at a preselected angle and engaging the adjacent one of saidplurality of laser discs to maintain said plurality of laser discs atsaid preselected angle, a lockring connected with said stop and readoutpilot, prism means received in said lockring for providing a path forthe transmission of energy and a fluid to said plurality of discs,sealing means between said lockring and said prism means for sealinglyengaging said jacket, and at least a groove in said stop and readoutpilot to provide for the flow of a fluid from said prism means to saidjacket through said bore.

5. A segmented laser apparatus as in claim 1, in which a retaining meansis received in each end of said jacket, whereby said laser apparatus maybe handled as a solid laser apparatus.

6. A segmented laser apparatus comprising an outer jacket having aninner wall defining a through bore, a plurality of laser discs in saidbore portions of which are in sliding engagement with said wall, each ofsaid discs comprising an active portion operable to transmit energy andan inactive portion, spacing means engaging the inactive portion of eachof said plurality of discs for maintaining said discs in spacedrelationship to each other, fluid passage means in said jacket forproviding a path for the flow of fluid therethrough, and retaining meansreceived in the respective ends of said jacket for retaining saidplurality of discs in said jacket, said inactive portion of each of saidplurality of discs comprising an inner active portion fabricated from alaser material and the inactive portion of each of said plurality ofdiscs comprising a surrounding inactive cladding portion.

7. A segmented laser apparatus as in claim 6, wherein cladding portionson opposite edges of adjacent discs are in spaced relationship tosaidinner wall of said jacket to define a portion of said fluid passagemeans therebetween to produce a serial flow of fluid through saidjacket.

8. A segmented laser apparatus as in claim 6, in which said spacingmeans comprises a plurality of bores in the cladding portion of at leasta face of each disc, and a respective pin received in each one of saidplurality of bores and extending therebeyond to engage the adjacentdisc.

9. A segmented laser apparatus as in claim 8, in which the external endsof the pins associated with each disc are coplanar.

10. A segmented laser apparatus as in claim 8, in which said pluralityof bores comprise three bores spaced about the active portion of saiddiscs.

11. A method for producing laser discs for a segmented laser apparatuscomprising forming a laser rod having an active inner laser portion anda surrounding cladding portion to a preselected diameter, removing aportion of the circumference of said rod to provide a relieved surface,cutting said rod into a plurality of discs at an angle to the axis ofthe rod as determined by the indices of refraction of the active portionof said rod and the fluid in which the discs are to be placed, polishingopposed faces of each of said plurality of discs, providing spaced boresin said cladding portion of each disc face, and inserting spacing pinsin each bore.

12. The method of claim 11, including the further step of making theends of said pins coplanar.

13. The method of claim 11, in which said removing step comprisesmounting said rod off-center, and grinding said rod to provide saidrelieved surface.

14. A method of producing a segmented laser apparatus comprisingproviding an outer jacket with a through bore, forming at least a firstand a second laser rod each having an active inner laser portionsurrounded by an inactive cladding portion to a preselected diameter,removing opposed portions of the respective circumferences of said firstand second laser rods to provide opposed relieved surfaces on said laserrods, cutting said-first and second laser rods at an angle with respectto the axis of the respective rods as determined by the indices ofrefraction of the active portion of said rod and the fluid in which thediscs are to be placed to provide a plurality of first discs and aplurality of second discs, polishing opposed faces of each of said discsafter cutting said discs, placing spaced bores in the cladding portionon the face of each of said discs, inserting pins into said bores toprovide spacers between adjacent discs, grinding and polishing the endsof said pins in each of said discs until said pin ends are coplanar,sequentially inserting said first and second discs into said jacketbore, and applying opposed compressive forces to said discs in said boreto bring said discs into rotational alignment.

15. The method of claim 14, including the step of closing the open endsof said jacket bore to maintain said discs in place.

16. The method of claim 14, in which said removing step comprisesmounting said first rod off-center in one direction and grinding saidfirst rod to obtain said relieved surface, and mounting said second rodoff-center in a second direction and grinding said second rod to obtainsaid opposed relieved surface.

1. A segmented laser apparatus comprising an outer jacket having aninner wall defining a through bore, a plurality of laser discs in saidbore, spacing means between adjacent ones of said plurality of discs formaintaining said discs in spaced relationship to each other, oppositeedges of alternate ones of said plurality of discs being spaced fromsaid wall to define alternating fluid paths therebetween whereby serialfluid flow is obtained through said jacket, and retaining means receivedin at least one end of said jacket for retaining said plurality of laserdiscs therein.
 2. A segmented laser apparatus as in claim 1, in whichsaid retaining means comprises fluid conduit means for providing apassage for the flow of fluid through said jacket.
 3. A segmented laserapparatus as in claim 1, in which said retaining means includes prismmeans comprising a prism having a first face extending beyond the edgeof said jacket and angulated at the Brewster angle determined by theprism and a fluid adapted to be in contact with said first face, and asecond face received within said jacket and angulated at the Brewsterangle determined by said prism and the fluid within said jacket, saidprism means further comprising a prism holder having a through boreadapted to receive said prism therethrough, the diameter of said prismholder through bore being slightly in excess of the diameter of saidprism whereby an annular fluid passage is formed therebetween, means insaid prism holder for providing for the flow of a fluid to said annularpassage, a radially extending flange on said prism, a shelf in saidprism holder adapted to provide a seat for said flange, and sealingmeans between said shelf and said flange.
 4. A segmented laser apparatusas in claim 1, in which said retaining means comprises stop meansincluding a stop and readout pilot having a rear edge at a preselectedangle and engaging the adjacent one of said plurality of laser discs tomaintain said plurality of laser discs at said preselected angle, alockring connected with said stop and readout pilot, prism meansreceived in said lockring for providing a path for the transmission ofenergy and a fluid to said plurality of discs, sealing means betweensaid lockring and said prism means for sealingly engaging said jacket,and at least a groove in said stop and readout pilot to provide for theflow of a fluid from said prism means to said jacket through said bore.5. A segmented laser apparatus as in claim 1, in which a retaining meansis received in each end of said jacket, whereby said laser apparatus maybe handled as a solid laser apparatus.
 6. A segmented lasEr apparatuscomprising an outer jacket having an inner wall defining a through bore,a plurality of laser discs in said bore portions of which are in slidingengagement with said wall, each of said discs comprising an activeportion operable to transmit energy and an inactive portion, spacingmeans engaging the inactive portion of each of said plurality of discsfor maintaining said discs in spaced relationship to each other, fluidpassage means in said jacket for providing a path for the flow of fluidtherethrough, and retaining means received in the respective ends ofsaid jacket for retaining said plurality of discs in said jacket, saidinactive portion of each of said plurality of discs comprising an inneractive portion fabricated from a laser material and the inactive portionof each of said plurality of discs comprising a surrounding inactivecladding portion.
 7. A segmented laser apparatus as in claim 6, whereincladding portions on opposite edges of adjacent discs are in spacedrelationship to said inner wall of said jacket to define a portion ofsaid fluid passage means therebetween to produce a serial flow of fluidthrough said jacket.
 8. A segmented laser apparatus as in claim 6, inwhich said spacing means comprises a plurality of bores in the claddingportion of at least a face of each disc, and a respective pin receivedin each one of said plurality of bores and extending therebeyond toengage the adjacent disc.
 9. A segmented laser apparatus as in claim 8,in which the external ends of the pins associated with each disc arecoplanar.
 10. A segmented laser apparatus as in claim 8, in which saidplurality of bores comprise three bores spaced about the active portionof said discs.
 11. A method for producing laser discs for a segmentedlaser apparatus comprising forming a laser rod having an active innerlaser portion and a surrounding cladding portion to a preselecteddiameter, removing a portion of the circumference of said rod to providea relieved surface, cutting said rod into a plurality of discs at anangle to the axis of the rod as determined by the indices of refractionof the active portion of said rod and the fluid in which the discs areto be placed, polishing opposed faces of each of said plurality ofdiscs, providing spaced bores in said cladding portion of each discface, and inserting spacing pins in each bore.
 12. The method of claim11, including the further step of making the ends of said pins coplanar.13. The method of claim 11, in which said removing step comprisesmounting said rod off-center, and grinding said rod to provide saidrelieved surface.
 14. A method of producing a segmented laser apparatuscomprising providing an outer jacket with a through bore, forming atleast a first and a second laser rod each having an active inner laserportion surrounded by an inactive cladding portion to a preselecteddiameter, removing opposed portions of the respective circumferences ofsaid first and second laser rods to provide opposed relieved surfaces onsaid laser rods, cutting said first and second laser rods at an anglewith respect to the axis of the respective rods as determined by theindices of refraction of the active portion of said rod and the fluid inwhich the discs are to be placed to provide a plurality of first discsand a plurality of second discs, polishing opposed faces of each of saiddiscs after cutting said discs, placing spaced bores in the claddingportion on the face of each of said discs, inserting pins into saidbores to provide spacers between adjacent discs, grinding and polishingthe ends of said pins in each of said discs until said pin ends arecoplanar, sequentially inserting said first and second discs into saidjacket bore, and applying opposed compressive forces to said discs insaid bore to bring said discs into rotational alignment.
 15. The methodof claim 14, including the step of closing the open ends of said jacketbore to maintain said discs in place.
 16. The method of claim 14, inWhich said removing step comprises mounting said first rod off-center inone direction and grinding said first rod to obtain said relievedsurface, and mounting said second rod off-center in a second directionand grinding said second rod to obtain said opposed relieved surface.